Windows Task Manager CPU usage vs VI Performance Monitors

[Box293]

This is probably a very obvious question but there is some debate about this with my co-workers.

When I view the Windows Task Manager it shows me the CPU history. Is this scale an accurate representation of the entire CPU on the ESX host or is it a representation of how much MHZ the ESX host is handing the guest at that point in time?

IE I have an Intel Xeon 3.0Ghz CPU in my virtual machine, when it is at 60% in the cpu history of task manager is that an accurate representation of 60% of the 3.0Ghz processor?

[kalex]

Its the representation of how much ESX host assigns to your Guest OS.

[spex]

It's dynamic I would guess - 2 examples:

ESX Host Idle:

CPU belongs nearly exclusive to a vm: 60% of Taskmanager should be equal 60% of phys. CPU

ESX Host heavily loaded and vm has low shares:

VM has a lot of read time, but is not scheduled. Taskmanager shows 100% but VM nearly gets no CPU. (you can make this lost cpu cycles visible with the optional desched process from vmware tools)

Regards Spex

[VirtualNoitall · Accepted solution]

Hello,

I would not use task manager as a definitive source for CPU performance for two reasons:

1) time keeping: http://www.vmware.com/pdf/vmware_timekeeping.pdf

2)each virtual processor, in each vm ,will only get a share of the total CPU available and can even be scheduled onto different processors ( but only one at a time per vcpu ) VI provides tools for tracking CPU usage on vms. I would use those numbers over what you can collect inside a vm.

[Box293]

Thanks for the answers. After reading the time keeping article I'll defiantly go through and disable windows time and configure VMware tools to do the time sync stuff.

I noticed there was some mention of shares, is there any documentation on this as I haven't really grasped this concept yet.

[kalex]

here you go:

http://www.vmware.com/pdf/vi3_30_20_resource_mgmt.pdf

[Box293]

Cheers, lots of good information in here.

Thanks